The specific goal of this proposal is to demonstrate the feasibility of detecting small tumors utilizing diagnostic ultrasound techniques with the aid of ultrasonic contrast agents. The tasks necessary to achieve this specific goal are: To identify and develop materials which are tumor specific and which also alter the ultrasonic characteristics of tissue. To determine the ultrasonic properties of selected materials and the differential uptake of selected materials in animal tumor models; To conduct appropriate clinical studies in order to characterize normal tissue, benign disease, and malignant neoplasia by ultrasound, and to compare the results obtained by the ultrasonic method to those of other diagnostic modalities including conventional x-rays (with and/or without contrast) and computerized tomography; to correlate all the results with the pathological specimen evaluation.